Are you referring to the black rear spoiler of the Micra SR? On the SR, there is an added spoiler over the white one, and it's black and includes the brake light. If that's what you want, you can contact any Nissan dealer and buy it and they will install it for you.
I have seen some really cool rear spoiler but it was from Japan and cost a fortune to order. I gave up. I have the SR so I do have the black spoiler.
This is the spoiler I am talking about from Japan :
And this is mine, stock from Nissan on the SR :
View my fuel log 2015 Micra SR automatic: 7.0 L/100 km ... 40.4 mpg (Imp) ... 14.3 km/L ... 33.6 mpg (US) ...